Casing running choke



ATTORNEYS P 1957 R. w. FARRAR CASING RUNNING CHOKE Filed June-l5, 1953 United States Patent G CASING RUNNING cHoKE Renard W. Farrar, Alvin, Tex., assignor to Phillips Petroleum Company, a corporation of Delaware Application June is, 1953, Serial No. 361,647 3 Claims. (Cl. 166-224) into the hole mud overflows from the top of the casing rather than from the annular space between the casing and the walls of the well.

To complete an oil or gas well many operators prefer to install a float shoe or float collar at or-near the bottom of the casing string. Such a shoe or collar contains a check valve which allows downward flow of fluid through the pipe but prevents upward flow. Although such a device has certain advantages there are also very serious disadvantages, particularly in certain areas and fields. When using a float valve one disadvantage is that'- it is necessary to interrupt the casing running process periodically to fill the casing with drilling fluid from above to prevent collapse of the pipe due to the weight of fluid in the annulus which is unbalanced from within the pipe.-

The loss of time occasioned by the filling operation is in itself a disadvantage but not as serious as the difliculty with stuck casing which in certain areas is likely whenthe casing running process is interrupted for more than very short intervals.

Another very serious disadvantage to the use of com Another disadvantage of filling the casing from the top is that air pockets may be entrained. These air pockets,

under critical conditions, can, when circulated into the annulus, lighten the column of mud sufliciently to cause a blowout. 7

Another disadvantage of filling the casing from the top is that in somecases plugging of the valve occursdue to settling out of lost circulation mud, cuttings, scale, etc.

Attempts have been made to solve the problems by using pressure controlled valves which allow filling from the bottom, but such have, in general, been unsatisfactory.

Usually the casing cannot be run completely open, since,

when the casing is nearly as large as the hole, i. e., the annulus between the casing and the walls of the well is small in comparison to the cross section of the casing, the displaced drilling fluid will flow'up and overflow on the drilling rig floor. I

fluid displaced by the casing being forced through through the casing Z,84,9Z8 Patented Sept. 3, 1957 lice According to my invention I have devised-an insertable restrictivecasing choke for admission of mud into thebottom of the casing during running of the casing. I further provide that such a choke, or orifice, may be constructed of any suitable and predetermined size depending upon the rate at which it is desired to flow the mud into Such chokes of.

the casing and on other conditions. different diameters may be assembled into the same or different diameter casings.

During running of casing at a given rate of speed, I

, have found that when my casing running choke apparatus of a predetermined desired size and discharge characteristics dependent upon the size of easing, depth to whichrun, size of hole, and flow properties of the mud, is inserted into the bottom of the casing, the mud enters the casing at a rate which will maintain the liquid level inside the casing at a point close to but below thederrick floor and will not permit the mud to overflow from the casing onto the derrick floor.

Anobject of my invention isto devise a simple casing running choke. Y

Another object of my invention is to provide a casing running choke apparatus in which choke orifices of .predetermined and desired sizes may be inserted.

Another object of my invention is to provide a casing running choke which is inexpensive to manufacture.

Still another object of myinvention is to provide a casing running choke for permitting faster running of well casing.

Yet' another object of my invention is to provide a simple casing running choke which can eliminate or re place the presently used complicated and difficult to operate equipment for controlling 'the flow of mud into the bottom of the casing during running operations.

Yet another object of my invention is to provide a simple casing running choke for controlling the flow of mud into the bottom of the casing without building up pressures within the well to a breaking point of weak formations.

Still other objects and advantages of my invention will be obvious to those skilled in the art upon reading the following specification and drawing, which respectively describes and illustrates preferred embodiments'of my invention. 7

In the drawing, Figure 1 is a longitudinal sectional view of one embodiment of my invention. a

" Figure 2 is an end view of the apparatus of Figure 1.,

Figure 3 is a longitudinal sectional view of another embodiment of my invention. g

Figure 4 is an end view of the apparatus of Figure 3.

Figure 5 is a longitudinal sectional view of an embodiment of my invention for use with a portion of the apparatus of Figure 3.

Figure 6 is a longitudinal elevational view' of still another embodiment of my invention which may 'be used with a portion of the apparatus of Figure 3.

Referring now to the drawing and specifically to Figure 1, reference numeral 11 identifies an elongated piece of tubing, a nipple or a collar having about the same diameter as that of the well casing. Threads 12 and13' should be of such size and'shape as to mesh operatively with a casing fitting or directly with threaded ends of casing sections. On the interior of the middle portion, longitudinally of this nipple 11 are corrugations 22.;An annulus of a plastic, resinous polymer or othermaterial 14 is provided in such a manner that it fits tightly and securely against corrugations 22. Preferably such material should be molded in place in the nipple 11. Another annulus 15 which may be of metal is provided with corrugations on its exterior surface to mesh with 'thecorrugations 22 of the material 14. g j A preferable method of manufacture is to insert a re movable plug, not shown, into the bottom end of the nipple 11 to such a point as desired for the bottom of the elements to be subsequently installed. After inserting such a plug the annulus 15 is placed upon this plug and properly positioned. A liquid material is then flowed nto the space between the outer corrugated surface of the annulus 1S and the inner corrugated surface of the nipple 11. This liquid material, after curing, on setting or hardening, forms the plastic or resin 14. Such. curing may be at atmospheric or elevated temperature, with or without added catalyst and at atmospheric or elevated pressure. After'this curing operation, the atorementioned plug, not shown onthe drawing, is removed and achoke tube 16 of predetermined inside diameter is inserted and: held in place by threads 17. The threads on the inner wall of the annulus 15 may be cut prior to the forming operation just described or they may be cut afterwards, as desired. One or more grooves may be cut in the outer wall of the choke tube 16 and. in the inner Wall ofthe annulus 15 foraccom modation of. Q-ring seals 18 and19. The ends of the choke tube 16 may if desired be beveled or rounded to form surfaces 20 and 21 to improve the flow characteristics of the insertable choke. tube 16.

In the use of such a casing running chokeasthatjust described the assembly may be installed on the bottom of the casing or. at a joint or two above the bottom, asdesired. When the choke tube16 of proper diameter has been installed in the nipple 11 and the nipple placed at or near the bottom of the casing string the casing may then be run into the well. During the casing running operation it is intended that the drilling mud should flow upward through the choke tube 16 at such a rate that the level-of the mud in thecasing will remain at apoint near but always below the drilling platform so as not to overflow thereon. If the choke tube 16 has too large a diameter, mud will enter the casing too rapidly and may overflow on the drilling platform. It the diameter. of the choke tube is too small the mud will not enter the casing sufficiently fast and the casing running operation will be undesirably retarded.

' To determine the proper size of choke tube 16, a calculation involving several variables must be made. A Sample calculation, illustrating the method of calculation which has been successful in field tests, follows:

=Drilling fluid density (lbs/gal.) 9.2 Ty=Drilling fluid yield value (lbs./ft. .0385v r=Drilling fluid rigidity (lbs/ft. sec.) .0097 L=Depth of hole (ft.).... 6942 V=Casing running speed (ft/sec.) 2 a=Averagc cross section of pipe (ft. .068 A=Average cross section of annulus (ft?) .392 Va=Equivalent fluid velocity in annulus (ft/sec.) (DA-T) =Diameter of annulus between casing and hole (in) t 4 D=Diameter of hole (in) ll do=0utside diameter of pipe (in) 7 di=Inside diameter of pipe (in) 6.06 g=Acceleration due to gravity (ft/sec?) 32.2

a i .068. I V,, V- 2 +.5-l.35

P,,=Pressure drop in annulus, lbs. per sq. in:

LT 32or-V L' 2.25(DAT) g(DAT 6942(.0385) 32(.()097)(1.35)(69=42) 225(4) 32.2(4) P,,=Pressure-d.rop in pipe, lbs-per sq. in.-

P Pressure drop across choke, lbs. per sq. in.=

P c=Diameter of choke, in,=2\/ p n6 Pcc Q=Quantity of fluid through choke (ftfi/sec.)

Di V

C= Discharge coeficient of ohoke= 0.9

Using the above illustrated method of .calculation the casing choke sizes used in the following examples were determined, and chokes of these sizes were used in running casings in the following wells:

In thesethree runs performance of the casing chokes was good in every respect.

If it. is desired to use my casing running choke as a shoe element on the bottom of the string of casing the choke element may take the form illustrated in- Figure 3. Inthis figure a resinous or plastic material 33 may be provided within pipe 31, as shown. The inside wall of this element 33 is threaded to accommodate the annulus or choke tube 3.4.. Reference numeral 37 is intended to identify the meshing threads. of the choke tube 34 and element 33. Corrugations 38 hold element 33 rigidly in place. At the bottom. end. of. thechoke tube 34isprovided a shoulder 36. which may be tightened when against agasket 39 so that the element 34 will not inadvertently become loosened. Slots 35 are provided for use of a tool fonremoving-or inserting choke tube 34. Threads32 areprovided at the upperv end of the pipe 31 for. fastening this apparatus to the end ofthestring of casing.

. Figure 5 is intended to illustrate a choke tube 44 pro vided with threads 47 and a shoulder 46 for insertion into the member 33 of Figure 3 in place of the choke tube 34. Slots 45 are for loosening or tightening this element. The choke tube of Figure 5 is intended to.be exactly-like the choke tube 34 of Figure 3 with the exception that its inside diameter is smaller. The use of such a choke tube of relatively small diameter would permit the running of a stringof casing at a slower rate than when choke tube 34 was used.

In Figure 6-is illustrated still another choke tube 54 in which the inside diameter is still smaller. This choke tube of Figure 6 is provided with slots 55, a shoulder 56 and threads 57 similar to those of the choke tubes of Figures 3 and 5.

, The choke apparatus of my invention may be used in running casing in wells in which it is desired to cement the casing. When a casing cement job is to be done the cement may be pumped into the casing in a conventional manner. When suflicient cement has been introduced a follow plug is inserted and mud is'pumpedinto the casing to lower the P s or; he cemen dow he casin out through tnecasing choke and up into the annulus between the casing and the walls of the well. The casing choke and its supporting elements are intended to be sufficiently rigid as to provide .a shoulder on which the cement follow plug may. rest. When the follow plug reaches this shoulder pressure is maintained on the mud in the casing until the cement has had ample time to set. After the cement has hardened to the desired extent and if it is desired to drill the well deeper the drill with its supporting tubing may be lowered into the Well and the cement follow plug and the choke tube and its supporting elements are drilled out and the well continued on down to any desired depth.

Since the choke tube and its supporting elements may need to be drilled out they should be made of a material which can be drilled out. Such material may be resinous or plastic material adapted to be cured either catalytically or noncatalytically. The elements supporting the choke tube may also be constructed of metal providing it can be drilled out by conventional oil well drills. Such metals as pewter, Woods metal, brass or other metal can be used provided it can be drilled out. It is obvious that steel should not be used since such metal could not easily be removed by an oil well drill.

The plastic, resin or metal element of Figure 3 may be cast-in-place in a manner described in relation to the annulus 14 of Figure 1. A blank may be used as a core to provide an axial opening throughout the length of element 33. After curing or hardening of this material the blank may be removed and the inner cylindrical Wall threaded to accommodate a threaded choke tube.

If it is not desired to drill a well deeper, after the cementing job the choke tube and its supporting elements may be left in the well. This latter condition would exist when the well had been drilled below an oil or gas producing formation. The casing would then be perforated adjacent the producing formation and the well produced in a conventional manner.

Example II =Drilling Fluid Density (lbs./ga1.) 9.2 T =Dril1ing Fluid Yield Value (lbs./ft. .07. 18 r=Drilling Fluid Rigidity (lbs/ft. sec.). 025). 021-. 032 L=Depth of Hole (it) 7, 000 7, 000 V= Casing Running Speed (ft/sec.) 1 a=Average Cross Section of Pipe (ft. 068 0G8 A=Average Cross Section of Annulus (it. 392 392 Vs=Equivalent Fluid Velocity in Annulus (ft./scc.) 673 2. (39 (DA T) =Diameter of Annulns Between Casing and Hole (in.) D=Diameter of Hole (in.) do=0utside Diameter 01 Pipe (in di=Inside Diameter of Pipe (in.) l. g=Acceleration Due to Gravity (ft./sec. Pa=1ressure Drop in Annulus, lbs. per sq.

The data of Example II obtained by the above illustrated method of calculation is illustrative of conditions in which casing running chokes of different sizes are adapted for use in running the same size casing into Wells of the same diameter and depth.

The calculated diameters determined above (Example II) are merely illustrative of one method of calculation. In commerce, such chokes might be made to the closest one eighth inch diameter. For example, the 1.022 inch diameter can be made the standard diameter of 1 inch, and the (b) example, 1.65 inch, can be made 1% inch.

Other suitable methods of calculation of the open diamii eter of a casing runiiing choke can be used. The herein given method is merely exemplary of one method which has been found satisfactory and reliable in practice.

Oneimportant advantage ofmy casing running choke is the reduced warehouseinyentory required. For any given size .of casingit ,is merely, necessary to maintain in stock an assortment of, ,sizesof orifice tubes such as tubes 16 and 34 of Figures 1 and 3, respectively. No other part of the apparatus is required to be stocked in quantity.

While certain embodiments of my invention have been described for illustrative purposes the invention is obviously not limited thereto.

I claim:

1. A deep well casing running choke assembly for use in running well casing in a deep well containing drilling mud comprising, in combination, a pipe, means for attaching the upper end of said pipe to a deep well casing, a rigid annular member disposed coaxially with respect to said pipe and rigidly aflixed to the inner wall thereof, a second rigid annular member disposed coaxially with respect to said first annular member and rigidly affixed to the inner wall thereof, and a third and removable rigid annular member having an unobstructed passageway of predetermined diameter and drilling mud flow characteristics disposed removably and rigidly within said second annular member so that drilling mud will not overflow the top end of the casing during casing running operations.

2. A deep Well casing running choke assembly for use in running well casing in a deep well containing drilling mud so that the drilling mud will not overflow the top end of the casing comprising, in combination, a pipe, means for attaching the upper end of said pipe to a deep well casing, a corrugation on the inner Wall of said pipe, 2 first rigid annular member having an exterior corrugation and being disposed coaxially with respect to said pipe and rigidly and immovably aflixed to the inner wall thereof, said corrugation on the outer wall of said annular member fitting the corrugation on the inner wall of said pipe, the inner wall of said annular member being threaded, a second and removable rigid annular member having, an unobstructed passageway of predetermined inner diameter and drilling mud flow characteristics being threaded within the threaded first annular member, and a seal intermediate the second annular member and the first annular member to seal against leakage of fluid therebetween.

3. A deep well casing running choke assembly for use in running well casing in a deep well containing drilling mud so that the drilling mud will not overflow the top end of the casing comprising, in combination, a pipe, means for attaching the upper end of said pipe to a deep well casing, a corrugation on the inner wall of said pipe, a first rigid annular member having an exterior corrugation and being disposed coaxially with respect to said pipe and rigidly and immovably aflixed to the inner wall thereof, said corrugation on the outer Wall of said annular member fitting the corrugation on the inner Wall of said pipe, a corrugation on the inner wall of said first rigid annular member, a second rigid annular member having an exterior corrugation and being disposed coaxially with respect to said first annular member and rigidly and immovably fixed to the inner wall thereof, said corrugation on the outer wall of said second annular member fitting the corrugation on the inner wall of said first annular member, screw threads disposed on the inner wall of said second annular member, a third and removable rigid annular member having an obstructed passageway of predetermined inner diameter and drilling mud flow characteristics being threaded within the threaded second annular member, and a pair of seals intermediate said third and second annular members sealing against leakage of fluid therebetween.

(References on following page) References Citedjnihe file Of this patent UNITED' STATES PATENTS McLaine Apr. 13, 1926 Greve May 29, 1928 5 'Baker Sept. 23, 1930 Burt Oct. 11, 1932 8 OLeary et a1. May 3, 1938 .Crowe11 June 6, 1939 T Kail Jan. 14, 1941 :Scaramu'cci Aug. 26, 1941 Schick June 4, 1946 Otis Oct. 16, 1951 Brown et a1. Dec. 28, 1954 

